Ownership

As expected, the MyNonEncodableType, &MyNonEncodableType, &mut MyNonEncodableType means the standard Rust ownership things - owned, borrowed, mutable borrowed. For example, in normal Rust, we cannot mutably borrow the same object twice at the same time. When doing so for RustAutoOpaque objects, you will receive a runtime error.

In short, just write normal Rust code, and you are safe. Anything that violates Rust's model or safety will be caught and provide a runtime error, instead of the dangerous undefined behavior.